1. Field of the Invention
This invention relates to an electrical contact ring for an electrochemical cell having an on-cell tester. More particularly, this invention relates to a contact ring for an electrochemical cell, such as a primary alkaline cell, having an on-cell tester to electrically connect one lead of the tester to the negative end terminal of the cell, and to a cell having such tester and contact ring.
2. Background of the Disclosure
The use of thermochromic voltage testers to visually indicate the condition of an electrochemical cell, commonly referred to as a battery, has become very popular and provides a value added advantage to the battery manufacturer and to the consumer. These testers are used with primary electrochemical cells, although they can also be used by consumers to test the condition of a secondary or rechargeable electrochemical cell if desired. The most popular tester presently in use is a thermochromic material in contact with an electrical resistance element which forms an integral part of a battery package in which the batteries are alkaline primary cells. The user places the terminals of the cell between the contacts of the tester and squeezes the contact ends of the tester to make electrical contact with the ends of the cell. The resistance element of the tester is heated in proportion to the cell voltage and the thermochromic material provides a qualitative indication of the condition of the cell over a range indicating "good" or "replace". This kind of tester is disclosed, for example, in U.S. Pat. No. 4,723,656. An integral, thermochromic package tester which can also be removed from the package is disclosed in U.S. Pat. No. 5,188,231. More recently, on-cell testers have been developed in which the cell condition indicator is an integral part of the cell label. These on-cell testers include both the thermochromic type and a new, electrochemical type of tester. An example of a thermochromic type of on-cell tester i disclosed in European Patent Publication No. 0 523 901 A1, the disclosure of which is incorporated herein by reference and which was published on Jan. 20, 1993. Unlike the thermochromic type which employs a resistance element to produce heat and which can therefore not be permanently attached to the terminals of the cell without continuously discharging it, the new electrochemical type does not draw current from the cell and can therefore be permanently, attached to the terminals of the cell without discharging the cell. This new type of tester is disclosed in U.S. Pat. No. 5,250,905. In either case, there is a need for a means to connect an on-cell tester to the negative end terminal without shorting across the end of the metal cell container which is the positive terminal.